Microstructure and properties of the Si3N4/silica aerogel composites fabricated by the sol–gel method via ambient pressure drying

• The sol–gel method was developed for preparing Si3N4/silica aerogel composite.
• The Si3N4/silica aerogel composites possess nanometer pore structures.
• The composite has both low thermal conductivity and dielectric loss tangent.
• The wave-transparent and thermal insulation functional integration was implemented.
• The composite can be made into complex shapes.

Si3N4 particle reinforced silica aerogel composites have been fabricated by the sol–gel method via ambient pressure drying. The microstructure and mechanical, thermal insulation and dielectric properties of the composites were investigated. The effect of the Si3N4 content on the microstructure and properties were also clarified. The results indicate that the obtained mesoporous composites exhibit low thermal conductivity (0.024–0.072 Wm− 1 K− 1), low dielectric constant (1.55–1.85) and low loss tangent (0.005–0.007). As the Si3N4 content increased from 5 to 20 vol.%, the compressive strength and the flexural strength of the composites increased from 3.21 to 12.05 MPa and from 0.36 to 2.45 MPa, respectively. The obtained composites exhibit considerable promise in wave transparency and thermal insulation functional integration applications.

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